Manifold Headers for MG MGB (1962-1980) 1.8L Engine

High-Flow Manifold Headers for 1962-1980 MG MGB (B-Series/ADO23)

What It Does: Replaces the restrictive factory cast-iron manifold and downpipe with a high-velocity 4-1 stainless steel system to improve exhaust scavenging and increase engine efficiency.

The Stock MGB Weakness

The factory exhaust manifold on the BMC B-Series engine is a significant performance bottleneck. Constructed from heavy cast iron, the OEM unit features a restrictive "log" design with rough internal casting flash that creates extreme turbulence and backpressure. These stock manifolds are also prone to heat-induced stress cracking over time, leading to persistent exhaust leaks and reduced power. Furthermore, the weight of the cast iron assembly adds unnecessary mass over the front axle, while its poor thermal dissipation properties contribute to excessive under-hood temperatures, which can lead to fuel percolation in the carburetors of these classic British roadsters.

The Engineering Solution

This 4-into-1 long-tube header is engineered to maximize the volumetric efficiency of the 1.8L B-Series engine. By utilizing tuned 1.50" primary tubes that merge into a high-flow 2" collector, this system uses exhaust pulse scavenging to effectively pull spent gases out of the combustion chamber. The construction features high-grade stainless steel for superior corrosion resistance and weight reduction. CNC-machined flanges provide a precision-flat mating surface to prevent leaks, while the combination of TIG and MIG welding ensures the structural integrity of the joints under high thermal loads. This design eliminates the "dead spots" found in the factory manifold, resulting in a dyno-proven gain of 5-10 HP and improved torque across the power band.

Technical Specifications

Compatibility

• MG MGB Roadster (1962-1980) 1.8L L4
• MG MGB GT (1965-1980) 1.8L L4
• Compatible with 18G, 18GA, and 18V Engine Series

The MG Standard

Designed for the European classic enthusiast, this header provides a precise fit for the ADO23 chassis without the need for complex fabrication. It delivers a visceral, classic exhaust note and sharper throttle response while maintaining the mechanical purity of the B-Series drivetrain. Perfect for owners looking to modernize their MGB’s breathing without sacrificing its vintage soul.

Common Questions

Will this exhaust header fit both my MG MGB Roadster and MGB GT?
Yes, this header fits 1962-1980 MG MGB Roadsters and 1965-1980 MG MGB GT models equipped with the 1.8L BMC B-Series inline-4 engine (18G, 18GA, and 18V engine series) on the ADO23 chassis.

What are the tube dimensions and construction specs of this header?
It features a 4-into-1 long-tube design built from stainless steel with 1.50" primary tubes merging into a 2" collector, CNC-machined flanges, and TIG/MIG welded joints.

What kind of power gains can I expect over the stock cast-iron manifold?
Replacing the restrictive factory cast-iron log manifold with this tuned 4-into-1 scavenging design delivers a dyno-proven gain of 5-10 HP along with improved torque and throttle response across the power band.

What is required to install this header on 1975-1980 North American models?
Because 1975-1980 North American models with the single Zenith-Stromberg carburetor use a combined 1-piece intake and exhaust manifold, installing a standalone header requires converting to a separate intake manifold such as a dual SU or Weber setup.

Does installing this header require custom exhaust fabrication?
It is engineered as a direct-fit replacement for the factory cast-iron manifold and downpipe on the ADO23 chassis without requiring complex fabrication.